Michelin Primacy 4 255/40 R18

Michelin Primacy 4 is a summer tyre made in total of 368 sizes, ranging from R14 to R14 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 255/40 R18 is 100mm wider than the narrowest dimension (155) and 50mm narrower than the widest one (305). This tyre profile of 40 means the sidewall height of the tyre is 40% of the tyre width (255mm), which results in 102mm sidewall height.